1. Field of the Invention
The invention relates to a pinch device for detecting a biomedical signal which pinches a finger, a nose, or an ear of a living body in order to detect a biomedical signal such as a pulse wave.
2. Related Art
FIG. 4 shows the configuration of an example of a prior art pinch device of this kind. Referring to FIG. 4, a pair of body members 1 and 2 are rotatably coupled to each other at their middle portions through a rotation shaft 3. The body members 1 and 2 are configured so as to be substantially symmetrical to each other with respect to the rotation shaft 3. The tip ends of the body members 1 and 2 are inwardly projected. Contact faces 1a and 2a are disposed at the projection ends so as to be opposed to each other, respectively. Driving portions 1b and 2b are disposed integrally with the rear ends of the body members 1 and 2 which are opposite to the tip ends with respect to the rotation shaft 3, respectively.
A substantially U-like spring member 4 is disposed on the outer peripheries of the body members 1 and 2 with placing the middle portion of the spring member at the rotation shaft 3. The ends of the spring member 4 are engaged with halfway positions between the tip ends of the body members 1 and 2 and the rotation shaft 3, respectively. These positions function as the points of application of the spring member 4. An LED 5 serving as a light emitting member, and a PD 6 serving as a light receiving member are embedded in the tip ends of the body members 1 and 2, respectively, and covered by a transparent resin so as to be flush with the contact faces 1a and 2a, respectively.
When a biomedical signal is to be detected by using the thus configured pinch device, the driving portions 1b and 2b are first inwardly pressed by fingers so that the contact faces 1a and 2a of the body members 1 and 2 are separated from each other. Next, a measuring site of a living body, for example, an ear 7 is inserted between the contact faces 1a and 2a and the driving portions are then released, so that the ear 7 is elastically pinched with the urging force exerted by the spring member 4. The LED 5 is then powered on and the PD 6 receives light transmitted through the ear 7 to detect a biomedical signal such as a pulse wave. Lead wires connected to the LED 5 and the PD 6 are not shown.
In the pinch device of the prior art configured as described, particularly when a measuring site of a living body is thick, the contact faces 1a and 2a of the body members 1 and 2 make point contact or line contact with the measuring site of the living body, so that the measuring site cannot be pinched by a uniform pressure. As a result, there arises a problem in that the pinch device is unstably attached and data of the detected biomedical signal are incorrect.